DESCRIPTION (Investigator's Abstract): Evolving brain edema after focal cerebral ischemia is associated with a post ischemic inflammatory response. Cardinal signs of acute inflammation have been noted in a stroke model featuring focal cerebral ischemia reperfusion. These include 1). infiltration of acute inflammatory cells (mostly polymorphonuclear neutrophils or PMNs); 2). endothelial cell (EC) injury reflected by an increase in vascular permeability; and 3). edema formation. The existence of a post ischemic inflammatory response is further supported by 2 lines of evidence: 1) accumulation of inflammatory mediators including kinins and eicosanoids in the ischemic brain; and 2). expression of cytokines and inducible nitric oxide synthase (iNOS). In this application we propose to further characterize the molecular events of this inflammatory process focusing on nitric oxide (NO) cascade. the specific aims are: 1. To study iNOS expression and changes in NO synthase (NOS) activity in relation to post ischemic inflammatory reaction and the evolution of brain edema. The hypothesis to be tested is that increase in iNOS expression and NOS activity contribute to post ischemic inflammatory process. Appropriate modulation of NO cascade may reduce the inflammatory reaction and brain edema. 2. To study the cellular mechanism of post ischemic iNOS expression. The hypothesis to be tested is that iNOS expression and NOS activity are enhanced by cell cell interaction (PMN EC, or EC glial). 3. To study in vitro the cellular and molecular mechanism of EC injury. The hypothesis to be tested is that activation of NO cascade contributes to EC injury under hypoxic/hypoglycemic condition; PMN and glial expression of iNOS accentuate EC injury. The overall objectives of this application are to define further the cellular and molecular mechanisms of post ischemic inflammatory reaction directed at NO cascade and to explore new therapeutic strategies that may reduce the extent of vasogenic brain edema after ischemic stroke.